164 part two engines and engine systemsThe engine-lubrication system is responsible fordistributing oil to all parts of the engine. While oil inthe engine reduces friction and prevents wear, it doesmuch more. Improved engine oils, together with thedesign of engine-lubricating systems, have generallyextended the periods between services and alsoincreased the service life of engines.

Figure 11.1 shows how the main parts of an engine arelubricated by oil pumped to them from the oil pan. Theoil reaches the various parts through pipes, passages,drillings, holes and grooves. These, together with the

oil pump, oil filter and oil pan, make up the lubricatingsystem of the engine.The main parts of the engine are provided withpositive lubrication, as shown. They receive oil directlyunder pressure, and so are referred to as being pressurefed. Other parts that are not as heavily loaded arelubricated with oil that is sprayed through a hole or jet.Some parts of the engine do not require pressurelubrication. These receive lubrication from oil on itsway back to the oil pan. Other parts depend on the oilmist that is present in the crankcase when the engine isoperating.

6. cleans.

figure 11.1

Oil minimises wearWith proper lubrication, all the parts that are subject towear are separated by a thin layer of oil. The oilprevents metal-to-metal contact so that there isminimum wear. This is illustrated in Figure 11.2 whichshows how oil is needed between the connecting-rodbearings and the crankshaft journals, and also betweenthe pistons and cylinder walls.Without proper lubrication, the bearings wouldwear quickly and eventually fail, causing damage tothe crankshaft and other engine parts.Shortage of oil on the cylinder walls would causeexcessive wear and scoring of the cylinders, pistonsand piston rings.

Lubricating oil from the oil pan is pumped throughout the engine

HYUNDAI

163-178_May_chap 11

12/9/06

9:56 AM

Page 165

chapter eleven engine-lubricating systems

165

Oil cleansAs it flows through the engine, the oil tends to carryaway any particles of carbon or foreign matter and takethem back to the oil pan. Heavier particles drop to thebottom of the oil pan. Lighter particles are removed bythe oil filter.Most of the cleaning is done by chemicaldetergents in the oil which keep engine parts clean,and by dispersants which hold particles suspended inthe oil so that they are not deposited on the internalparts of the engine.

Oil circulationfigure 11.2

Oil fills the very small irregularities in thesurfaces – it reduces friction in bearings andhelps seal pistons and rings

Oil reduces friction and power lossAll the moving parts of the engine are provided withoil, and this reduces the friction between surfaces thatare in contact. Less friction means less power losswithin the engine.There is still some friction in the engine, but this isfluid friction between the layers of oil, and is muchless than dry friction.

The lubricating system of an overhead-camshaftengine is shown as a block diagram in Figure 11.3. Thearrows show how the oil flows in the various parts ofthe system.Figure 11.4 is a similar lubricating system, but thisis an engine diagram, which shows how the oil reaches

Oil removes heatThe oil is being continuously circulated throughout theengine, and while it lubricates the various parts, it alsoremoves heat from them and carries it back to the oilpan. Heat from the oil pan is dissipated into thesurrounding air.Some engines are fitted with an oil cooler. This isused to transfer heat from the engine oil to the coolingsystem, or to the atmosphere. This reduces the oiltemperature.Oil reduces engine noiseThere is always some clearance between the bearingsand journals, and between other working parts. Whenthe load on a part is suddenly increased, the oilbetween the parts acts as a cushion to absorb the shockand reduce the noise.Oil forms a sealPiston rings must form a gas-tight seal between thepiston and the cylinder wall. The oil on the cylindershelps by filling the very small irregularities in thesurfaces. At the same time, the oil on the cylinderwalls lubricates the pistons and rings.

the actual engine parts. In both diagrams, oil flowstarts at the oil pan and, after circulating through theengine, returns to the oil pan.The various parts of the lubricating system arelisted below. Using this as a reference, the oil flowshould be followed through the block diagram and alsothrough the engine diagram.Oil circulates through the lubricating system asfollows:1. Oil pump. The oil pump is driven by the engine. Ittakes oil from the oil pan through the strainer andsuction pipe and delivers it to the filter. The

strainer prevents foreign matter from reaching thepump.2. Relief valve. The relief (or regulator) valve regulates the pressure in the system. When the pressurespecified for the engine is reached, the relief valveopens to prevent any further increase in pressure.Surplus oil is then bypassed to the intake side of thepump.3. Oil filter. All the oil which leaves the pump isfiltered before entering the engine. The filterremoves particles of carbon and any other matter inthe oil and so protects the engine.

163-178_May_chap 11

12/9/06

9:56 AM

Page 167

chapter eleven engine-lubricating systems

The filter has a bypass valve which opens if thefilter becomes blocked. This allows unfiltered oil topass into the system so that the engine is notstarved of oil.4. Main oil gallery. The main oil gallery is a passagethat runs the full length of the crankcase. A numberof drillings and passages from the gallery serviceother parts of the lubrication system.In Figure 11.4, a passage from the main oilgallery carries oil to the overhead camshaft andvalve gear, and a drilling through each of thecrankcase webs supplies oil to the main bearings.5. Crankshaft main bearings. Each of the five mainbearings is supplied with oil through a separatedrilling from the main oil gallery.6. Connecting-rod bearings. Drillings in thecrankshaft carry oil from the main bearings tothe connecting-rod bearings. Some oil leaves theconnecting-rod bearings and is thrown around as amist, and this helps to lubricate the internal parts ofthe engine.7. Oil jet. An oil jet is used to lubricate the cylinderwalls and pistons (Figure 11.5). A small hole in theside of the connecting rod is arranged to line upwith the oil drilling in the crankpin journal. As thisoccurs, a spray of oil is directed onto the cylinderwalls. This happens once in each crankshaftrevolution.8. Camshaft bearings. The camshaft receives its oilsupply from the main oil gallery. In the arrangementshown in Figure 11.4, there are separate rockershafts for the intake and exhaust valves. The oil tolubricate the camshaft bearings is carried throughthe hollow rocker shaft to the camshaft bearing caps,where drillings take it to the camshaft bearings.

167

9. Rocker shafts. Drillings in the rocker shaftsprovide oil to the rocker arms and these, in turn,have a small drilling to provide lubrication to thecams (Figure 11.6).rocker arm

oil in shaft

oil drillingcamshaft

oil pool oncylinder head

figure 11.6

Lubrication of rocker arms and cams

MAZDA

10. Cams. As well as receiving oil directly from therocker arms, the cams and the other parts arelubricated by splash. The cylinder head under thecamshaft is shaped to form an oil reservoir fromwhich oil is splashed by the cams to lubricate thecam surfaces, valve stems and valve springs.11. Timing chain. Where a timing chain is fitted, oil isprovided from the end camshaft bearing or similarsource so that the chain and sprockets arelubricated.12. Return oil. After lubricating the variouscomponents, oil from the cylinder head drainsback to the oil pan through oil drain holesprovided for this purpose. Oil from the crankshaftdrops directly back to the oil pan.

When a hole in the connecting rod aligns witha hole in the crankpin, oil is sprayed onto thecylinder wall to lubricate the piston and rings

■ Oil pumps can be driven by gears or by a chain, ordirectly from the crankshaft.

163-178_May_chap 11

12/9/06

9:56 AM

Page 168

168 part two engines and engine systemsdriven gear

crescent

outer gear

inner rotor

outer rotor

housing

housing

innergear

drive gear(a) Gear pump

figure 11.7

(b) Crescent pump

(c) Rotor pump

Three basic designs of oil pumps

Gear pumpsA gear pump, as shown in Figure 11.8, has two gears:a drive gear and a driven gear. The drive gear is fixedto a shaft and is driven by gears from the engine’scamshaft. The driven gear is mounted on a stationaryshaft and is rotated by the drive gear.

When assembled, the gears are contained within thepump body by the lower cover. The strainer is attachedto the pump inlet, which is part of the cover, andimmersed in oil in the oil pan.In operation, oil enters the pump inlet through thestrainer and is carried around between the gear teethand the body of the pump to the outlet, where it isdelivered from the top of the pump into the lubricatingsystem.Crescent pumpThe crescent pump shown in Figure 11.9 has anexternal toothed gear meshed with an internal toothedgear. Some of the teeth of the gears are in mesh, butthe others are separated by a crescent-shaped part ofthe pump housing.The pump is mounted on the front of the crankcasewith the inner gear on the end of the crankshaft, so thatthe pump is driven directly from the crankshaft.When the pump is operating, oil is taken in throughthe intake port and is carried around between the gearsand the crescent to the outlet port.■ The oil pump of the engine-lubricating systemshown in Figure 11.4 is a crescent-type pump.Rotor pump

The pump housing is bolted to the front of thecrankcase. It has an inner rotor and an outer rotor(Figure 11.10). The inner rotor is mounted on thecrankshaft and so rotates whenever the engine isrunning. The lobes of the inner rotor fit into the outerrotor which is rotated in the housing.

163-178_May_chap 11

12/9/06

9:56 AM

Page 169

chapter eleven engine-lubricating systems

169

An example of checking the clearance of the gearsin the housing is shown in Figure 11.9, where feelergauges are being used between the gear and thehousing.Oil pump relief valve

figure 11.9

Crescent oil pump – clearance can bechecked where shown and also between thegears and crescent MAZDA

The oil pump is capable of supplying much more oilthan is needed to maintain a pressure in the lubricatingsystem. To prevent excessive pressure developing, arelief valve is fitted to the oil pump or to the oilgallery.The relief valve consists of a spring and plunger,which opens and closes a port to regulate the flow ofoil. A simplified relief valve is shown in Figure 11.11.It works like this:1. When the engine is started, the pump supplies oil tothe system. At engine idle speed, the port is closedby the plunger. All the oil from the pump enters thesystem and provides a low oil pressure.2. As engine speed increases, the pump speed alsoincreases and so more oil is delivered into thesystem. This increases the pressure in the system.Pressure acting on the top of the plunger moves itdown its bore.3. When the system reaches a certain pressure, whichis determined by the strength of the plunger spring,the plunger will have moved far enough to open theport.4. Surplus oil, which is not needed to maintainpressure in the system, will then pass through theport and return to the intake side of the pump.

5. The plunger will open and close the port, as needed,to release surplus oil and limit the pressure in thesystem. Whether the port is open or closed will

Oil is taken into the pump through an inlet pipe andstrainer and carried around between the lobes of therotors to the outlet port. A relief valve in the pumpbody controls the pressure in the system.

Oil pump serviceUnder normal circumstances, an oil pump would onlybe serviced during a complete engine overhaul.The pump and regulator valve would be cleaned,and the gears and housing checked for scores andwear. The clearance between the gears and housing (orrotor and housing) would be checked, as well as theend clearance of the gears in the housing.

figure 11.11

Operation of an oil pressure relief valve –pressure on top of the plunger is opposed bythe spring

163-178_May_chap 11

12/9/06

9:56 AM

Page 170

170 part two engines and engine systemsdepend on the engine speed and the temperature ofthe oil. It will also depend on the condition of theengine.■ A relief valve is located in the housing of the oilpump shown in Figure 11.10.Why the system has pressurePressure builds up in the system because the oil pumpmaintains a supply of oil, and also because of therestrictions provided by the small bearing clearancesetc, which prevent the oil from flowing readily back tothe oil pan.With worn bearings and large clearances, or if arelief valve is stuck open or has a faulty spring, thepressure in the lubricating system will be low. If any ofthese conditions occurs, the pump will be delivering toits maximum capacity but will not be able to supplyenough oil to build up normal pressure.■ Oil pressure depends on the pump delivering anadequate supply of oil and the engine being in goodmechanical condition. A badly worn engine willhave low oil pressure.

figure 11.12

Construction of a canister-type oil filter

Oil filtersDuring engine operation, carbon particles, dust andsmall metal particles become mixed with thelubricating oil. The oil filter keeps the oil clean byremoving these impurities which would otherwise findtheir way through the oil passages to the bearings andother surfaces.A sectioned oil filter is shown in Figure 11.12. Itconsists of a metal canister with a pleated-paperelement. The element is porous to allow oil flow without restriction, but the pores are fine enough to filter outthe impurities in the oil. The canister is threaded on to atubular mounting on the engine block. A rubber ringprovides a seal between the filter and its mounting.The filter has a non-return valve at the open end ofthe canister which prevents oil from draining from thefilter when the engine is stopped. The valve is a rubberdisc that covers a ring of holes.When the engine is running, oil flows into the filterthrough the non-return valve holes to the outside of theelement. It passes through the element to the inside ofthe canister, then back to the engine through thetubular mounting.A bypass valve inside the canister is a safety valve,which opens to allow oil to go straight through thefilter should the element become blocked.

Replaceable filter elementThe filter assembly in Figure 11.13 has a replaceablefilter element. The filter housing is bolted to the engineblock and the paper element is held in the housing bythe filter cover.The oil flow in the filter is similar to that of acanister filter.cover

O-ring

filter element

housing

sealing ring

figure 11.13

Oil filter with a replaceable elementHOLDEN LTD

163-178_May_chap 11

12/9/06

9:56 AM

Page 171

chapter eleven engine-lubricating systems

Full-flow and bypass filtersThere are two filter arrangements: full-flow filtersand bypass filters. Full-flow filters are mainly used,but some diesel engines have a full-flow filter as themain oil filter, and a bypass filter as a supplementaryfilter.Full-flow filterFigure 11.14 shows the principle of a full-flow oilfilter. All the oil delivered from the pump passesthrough the filter on its way to the bearings and otherengine parts, so that only filtered oil is used forlubrication. A bypass valve is located in the filter sothat if the filter becomes clogged, the valve will openand oil will still be supplied to the system.■ Full-flow filters operate at engine oil pressure andmust be correctly tightened during servicing toavoid oil leaks.Bypass filterThe principle of a bypass filter is shown in Figure11.15. This filters only a portion of the oil delivered

figure 11.14

Principle of a full-flow oil filter – all the oilentering the system is filtered

figure 11.15

Principle of a bypass filter – some of the oilfrom the pump is filtered and returned to theoil pan

171

from the pump to the oilways of the engine and itoperates at a lower pressure than a full-flow filter.An oil line is tapped into the oil gallery and arestricted amount of oil is allowed to flow through thefilter. The oil from the filter is not delivered into theengine, but is bypassed and returned to the oil pan. Inthis way, some oil is always being filtered, though notdirectly on its way to the engine parts.

Oil coolersOil coolers are heat exchangers, in which heat in theoil is transferred either to the engine coolant, or to theatmosphere.There are two designs of oil coolers:1. oil-to-coolant coolers2. oil-to-air coolers.Oil-to-coolant oil coolerBoth oil and coolant flow through this type of cooler,the two being separated by tubes or baffles of sometype. This enables heat to be transferred from the oil tothe coolant because the oil is at a higher temperature.An oil cooler and oil filter assembly for a smalldiesel engine is shown in Figure 11.16. Both the coolerand the filter are installed on the oil filter mounting onthe cylinder block. With this arrangement, oil from theoil gallery passes through the oil cooler before it enters

figure 11.16

Oil-to-coolant type oil cooler and oil filterassembly FORD

163-178_May_chap 11

12/9/06

9:56 AM

Page 172

172 part two engines and engine systemsthe filter, so that oil leaving the filter has been bothcooled and filtered.The cooler has external connections for the coolanthoses that connect it to the engine’s cooling system.

heat is removed from the oil and its temperature isreduced.The cooler is located in the engine compartmentwhere it will get an adequate flow of air, usually nearthe radiator.

Oil-to-air oil coolerThis type of oil cooler is similar to a radiator in thatit has tubes and fins (Figure 11.17). Oil from thelubrication system is circulated through the cooler, andair is directed across the tubes and fins. In this way,connecting hoses

oil inlet

Lubrication system with oil-to-coolant coolerA lubricating system for a small diesel engine is shownin Figure 11.18. This has an oil-to-coolant type cooler.The cooler is mounted to the engine block and the oilfilter is mounted on the cooler. Oil flows through thecooler, then through the oil filter and on to the main oilgallery.This system has other features that can be identifiedin the illustration:1. The oil pump is directly driven by the engine. It isa rotor pump, referred to as a trochoid-type gearpump.2. The engine has balance shafts with bearings that arepressure-fed from the main oil gallery.3. The engine has a timing chain which is suppliedwith oil from oil jets.

oil outlet

4. The system has piston-cooling jets which squirt oilupwards into the pistons to cool the piston head.

air flowoil cooler

5. The engine valves have hydraulic tappets which aresupplied with oil from the rocker shafts on top ofthe cylinder head.

figure 11.17

Oil-to-air type oil cooler

figure 11.18

Engine lubricating system with an oil cooler and other features

TOYOTA

FORD

163-178_May_chap 11

12/9/06

9:56 AM

Page 173

chapter eleven engine-lubricating systems

V-type engine lubrication systemFigure 11.19 shows the lubricating system for a V-typepetrol engine. This has a lot of overhead gear, including two camshafts on each cylinder head. Oil has to besupplied to four camshafts and also to the camshaftgears.The lubricating system includes an oil-to-coolantoil cooler.Turbocharger lubrication

173

1. Dry friction. Dry friction occurs between drysurfaces. The lubricants used with bearings and onsliding surfaces are used to convert dry friction tofluid friction.2. Fluid friction. This is much less than dry frictionbecause the lubricant separates the movingsurfaces. Lubricated surfaces have some friction,due to the molecules of oil which have to bemoved, but this is small compared to the friction ifthe surfaces are dry.

Oil coolers are fitted to engines with turbochargers.Turbochargers rotate at high speeds and are alsosubjected to exhaust heat. For these reasons, a constantflow of oil is provided to the turbocharger bearings toboth cool and lubricate.An oil line from the oil gallery delivers the oil tothe turbocharger and a drain pipe returns the surplusoil to the oil pan.

3. Boundary friction. This is a condition between dryfriction and fluid friction, where the surfaces arealmost unprotected, being coated only by an oilyfilm. The surfaces are actually in contact and arenot separated by a layer of oil.

Lubrication of engine bearings

■ Engine parts rely on boundary lubrication for ashort time when the engine is first started, before allthe lubricating passages have had time to fill. This isa critical period that is responsible for engine wear.

The main purpose of a lubricant is to convert dryfriction to fluid friction. These and associated terms areused in relation to lubrication and bearings as follows:

4. Boundary lubrication. The term is used in relationto the very small amount of lubricant (or oil film)that is on a shaft and bearing under boundaryfriction conditions.

camshaft gearsL.H. camshaftsR.H camshafts

oil cooleroil pump

oil filter

pump inlet

oil pan

oil strainer

figure 11.19

Lubricating system for a V-type engine – it has an oil-to-coolant oil cooler

TOYOTA

163-178_May_chap 11

12/9/06

9:56 AM

Page 174

174 part two engines and engine systemsHow engine bearings are lubricatedBearings like the crankshaft bearings are supplied withoil under pressure from an oil pump. The pressure oildoes not, as might be imagined, merely lift the shaftoff the bearings and cause it to float on the oil – therotation of the shaft is responsible for this. The shaftcollects layers of the oil delivered to the bearing andcarries them around with it.The layers of oil are wedged between the shaft andthe bearing, so that the shaft is forced to rise (or float)on the oil. Therefore it is shaft rotation that causesfloating to occur to prevent metal-to-metal contact, andnot the fact that oil is being delivered from the pumpunder pressure. This is known as hydrodynamiclubrication.In engine lubrication diagrams, it can be seen thatthe oil to the main crankshaft bearings enters at the top,and so it cannot force the shaft upwards off the bearing. There is a very small clearance between thecrankshaft journal and its bearings, but it is sufficientfor hydrodynamic lubrication to take place.Bearing, shaft and oil wedgeFigure 11.20 shows in sequence, from (a) to (d), theaction of a shaft as it commences to rotate in a bearingand build up an oil wedge. The clearances between theshaft and the bearing in the illustrations areexaggerated to show this effect to advantage.1. The shaft is stationary (Figure 11.20(a)). X indicates the area where only a thin film of oil coversthe shaft and bearing. This is the stage at whichboundary lubrication (and boundary friction) arepresent.2. When the shaft commences to rotate (Figure11.20(b)), it rolls to contact the bearing at Y. This isstill only boundary lubrication.

figure 11.20

Principle of lubrication of a shaft and bearing – the shaft rotates in an anticlockwisedirection

There is a thick layer of oil at the top, but littleoil at the bottom. As the shaft rotates, it acts like anoil pump, causing pressure to build up at Y. Thisforces the shaft towards the centre of the bearing.3. The shaft speed has increased and it has picked uplayers of oil (Figure 11.20(c)). The shaft has beenforced over to the right so that it is now surroundedin oil.4. The shaft runs floating on oil (Figure 11.20(d)).Pressure due to rotation is greatest at Z, and thiskeeps the shaft away from the bearing.

Crankcase ventilationCrankcase ventilation is provided to remove vapoursfrom the crankcase and prevent their harmful effects.Although ventilation is not directly a part of thelubricating system, the engine oil would deteriorate ifthe engine did not have an effective ventilating system.During normal engine operation, some combustiongases leak past the piston rings – this is called blowby.Without ventilation, this would tend to pressurise thecrankcase. There could be traces of water, and someunburnt fuel could reach the crankcase. All thesewould have a deteriorating effect on the engine oil andalso on mechanical parts.Early ventilation systems merely vented thecrankcase to the atmosphere, but this contributed to airpollution. It was an inefficient method of ventilationand did not keep out dust. Closed-crankcase ventilationsystems were therefore developed, and these becameknown as positive crankcase ventilation.Positive crankcase ventilationThe principle of positive crankcase ventilation (PCV)is shown in Figure 11.21. This is a V-type engine.There is an air hose from the clean-air side of theengine’s air filter to the right valve cover, and avacuum hose which connects the PCV valve on the leftvalve cover to the intake manifold.Clean air is drawn into the crankcase, where itmixes with the blowby gases. The gases are thendrawn from the crankcase through the PCV valve andthe vacuum hose into the intake manifold. They arecarried into the combustion chambers of the engine,where they are burnt.PCV valveThe positive crankcase ventilation valve (PCV valve)is a flow-control valve that is fitted between the

163-178_May_chap 11

12/9/06

9:56 AM

Page 175

chapter eleven engine-lubricating systems

figure 11.22

175

The level on the dipstick should be checkedcarefully TOYOTA

Changing the engine oil and filterfigure 11.21

Positive crankcase ventilation (PCV) system

The general procedure for changing the oil and filter isas follows:1. Warm up the engine.

crankcase and the manifold. It controls the air enteringthe intake manifold at engine idle speed, so thatexcessive air does not enter the manifold to upsetengine idling.If this valve does not seal properly, or remainsopen, the engine will idle badly.If the valve sticks closed, harmful vapours willremain in the crankcase to form acids, sludge etc andgive poor lubrication. Correct operation of this valve isessential. If it sticks either open or closed, it should becleaned or replaced.■ Crankcase ventilation is covered in Volume 2 withother emission controls.

Lubricating-system maintenanceLubricating-system maintenance consists of keeping acheck on the level of oil in the oil pan by means of thedipstick, carrying out regular oil and filter changes,and checking for possible oil leaks.Dipstick checkThe oil level on the dipstick should be checked withthe vehicle in a level position, not on a slope. Removethe dipstick, wipe it clean and also wipe the top of thedipstick tube to remove dust. Reinsert the dipstick andagain remove it to check the level.The oil level should be between the high and thelow marks, but close to the high mark (Figure 11.22).Top up if necessary, but do not overfill.■ Using the dipstick to check the engine oil level is asimple check, but one that is most important.

2. Remove the oil filler cap from the valve cover.3. Remove the drain plug from the oil pan and drainthe oil into a suitable container.4. Check the condition of the plug washer, wipearound the plug hole and replace the plug. Tightenfirmly, but do not overtighten.5. Remove the oil filter and replace with a new one.6. Pour sufficient oil into the filler hole in the valvecover to show on the dipstick.7. Start the engine and run it slowly until the filter fillsand the oil pressure warning light goes out, thenstop the engine.8. Check the level of the oil on the dipstick and top upto the full mark. The vehicle should be level.9. Run the engine and check the filter seal for leaks.Make a final check of the oil level.■ Use the correct type and grade of oil recommendedby the vehicle manufacturer. (Lubricants arecovered in Chapter 32: Fuels, fluids and lubricants.)Servicing oil filtersMost filters consist of a metal canister containing afilter element. These are sometimes referred to as‘throw-away’ filters because the complete filter isunscrewed from its mounting on the engine and a newone fitted in its place (Figure 11.23.)An oil filter removing tool is shown in Figure11.24. This has a band that fits around the filtercanister. The band tightens onto the canister as it isbeing used, enabling the filter to be unscrewed from itsmounting.

163-178_May_chap 11

12/9/06

9:56 AM

Page 176

176 part two engines and engine systems

figure 11.23

Replaceable oil filter that is threaded on toits mounting

figure 11.24

An oil filter removing tool

MAZDA

Oil filters should be replaced at specified serviceperiods, for example, each 10 000 kilometres. Wheninstalling a canister-type filter, observe the following,as shown in Figure 11.25:1. Clean the filter mounting.2. Coat the rubber seal with oil.

figure 11.25

Installing a canister-type oil filter

DAIHATSU

3. If possible, fill the filter with oil before fitting.4. Screw the filter into place until the seal contacts themounting surface.5. Tighten, by hand, an extra one-half to threequarters of a turn.

element. The old filter element is discarded and, aftermaking sure that the filter housing is clean, a new filterelement is installed.

6. After running the engine, check for oil leaks.

Checking oil leaks

For a replaceable-element type filter, the outercover of the filter is removed to gain access to the filter

The most likely places for oil leaks are the oil filter,the valve cover, and the oil pan. Where oil has coated

163-178_May_chap 11

12/9/06

9:56 AM

Page 177

chapter eleven engine-lubricating systems

177

the engine and the leak is not easy to find, clean theengine and then run it until the oil is warm. With theparts of the engine clean and the oil thin, leaks shouldbe easier to find.Oil pressure testTo check the oil pressure in the system, remove the oilpressure switch from the engine block and install anoil pressure gauge (Figure 11.26). Check the pressureat idle and at higher engine speeds. Check the pressurewhen the engine is hot and also when it is cold.Low pressure could be caused by a broken reliefvalve spring, a worn pump not providing enough oil,or worn engine bearings allowing too much oil flow.High pressure could be due to a stuck relief valve.

figure 11.27

Testing an oil pressure warning-light switchMITSUBISHI

table 11.1 General lubricating-system problemsPROBLEM

POSSIBLE CAUSE

Frequent topping up

Oil leaksOil being burnt because ofworn engine

Oil leaks

Loose boltsFaulty gasket or sealFilter not tightLeak at the drain plug

Oil pan overfull

Coolant leak into cylindersOverfilled when topping up

figure 11.26

Emulsified oil

Coolant mixed with the oil

Sludgy oil

Incorrect oil

Pressure gauge connected to check theengine oil pressure DAIHATSU

Badly worn piston ringsFaulty crankcase-ventilatingsystem

Warning-light switchThis is a pressure-operated switch that is screwed intothe main oil gallery. The switch will be ‘on’ when theengine is stopped and there is no pressure in thesystem. It will be switched ‘off’ by the pressure inthe system once the engine is started.The switch can be checked with a test lampbetween the terminal and earth as shown in Figure11.27. The lamp should light with the engine stoppedand go off when the engine is started.If the switch is in order, the problem could be ablown bulb or a faulty connection.